Following his family tradition of military service, he enrolled in the Academy of Infantry and Cavalry of Modena at the age of 18, thus beginning his career in the Royal Italian Army.

[2] In the buildup to World War II, Prince Amedeo, Duke of Aosta gave Guillet command of the 2,500-strong Gruppo Bande Amhara, made up of recruits from throughout Italian East Africa, with six European officers and Eritrean NCOs.

The "Gruppo Bande Amahara" has suffered 826 deaths and more than 600 injured from the beginning of WW2; it had no deserters and received the gold medal in the memory of the heroic Togni, and high praise from our enemies, written in the official reports of the British High CommandIl Gruppo Bande Amahara ha avuto 826 morti e più di 600 feriti dall'inizio della guerra, nessun disertore e la medaglia d'oro alla memoria dell'eroico Togni e gli ammirati elogi del nemico, nelle relazioni ufficiali dello Stato Maggiore Britannico.Guillet's most important battle happened towards the end of January 1941 at Cherù when he attacked enemy armoured units.

The battles and skirmishes in which this young lieutenant was a protagonist (Guillet commanded an entire brigade, notwithstanding his low rank) are highlighted in the British bulletins of war.

Official documents show that in January 1941 at Cherù "with the task of protecting the withdrawal of the battalions ... with skillful maneuver and intuition of a commander ...

Guillet, ... in a particularly difficult moment of this hard fight, guided with disregard of danger, an attack against enemy tanks with hand bombs and benzine bottles setting two on fire while a third managed to escape while in flames."

To the end of his life, the "Devil Commander" used words of deep respect and admiration for that proud population to whom he felt indebted as a soldier, Italian, and man.

His actions served their intended purpose and saved the lives of thousands of Italians and Eritreans who withdrew into the territory better known as the Amba Alagi.

A little more than a year later a friend of Guillet, Colonel Bettoni, launched the men and horses of the "Savoia Cavalry" against Soviet troops at Isbuchenskij.

[6] Later (in early 1942) for security reasons he changed his name to Ahmed Abdallah Al Redai, studied the Koran and looked like an authentic Arab: so when British soldiers came to capture him, he fooled them with his new identity and escaped on two occasions.

After numerous adventures, including working as a water seller, Guillet was finally able to reach Yemen, where for about one year he trained soldiers and cavalrymen for Imam Yahya's army, whose son Ahmad became a close friend.

Despite the opposition of the Yemenite royal house, he succeeded in embarking incognito on a Red Cross ship repatriating sick and injured Italians and finally returned to Italy a few days before the armistice in September 1943.

On 25 April 1945, he was entrusted as a secret agent with the mission to recover the crown of the Ethiopian negus from the "Garibaldi" partisan brigade, which had stolen it from the Social Republic.

Following the war, Guillet entered the Italian diplomatic service where he represented Italy in Egypt, Yemen, Jordan, Morocco, and finally as ambassador to India until 1975.

On 4 November 2000, the day of the Festivity of the Armed Forces, Guillet was presented with the Knight Grand Cross of the Military Order of Italy by President Carlo Azeglio Ciampi.

[8][9] In 2003, Amedeo reunited with one of his old wartime adversaries when he invited Lt Kenneth Simonds, the British officer who had faced his cavalry charge in command of an artillery battery, to his farm in County Meath.